Illinois income tax calculator

Most people know their marginal rate and almost nobody knows their effective rate. The two are rarely close. A single filer on $90,000 sits in the 22% bracket in 2026 and pays about 12.19% of that income in federal tax, because the first $16,100 is covered by the standard deduction and the next $38,000 is taxed at 10% and 12%.

The tool above shows both numbers, plus the band by band arithmetic that produces them. It also shows where it will not give an answer, which matters more than the places where it will.

What income figure should I enter?

Enter your income before the standard deduction. The field is labelled Annual income, before deductions because the engine subtracts the 2026 standard deduction for your filing status before applying any bracket. Entering an already reduced figure deducts it twice and understates the bill. If you itemize, enter income minus your itemized total instead.

The three inputs are Annual income, before deductions, Filing status and State. There are no fields for credits, dependents or above-the-line deductions.

How this calculator works

Federal tax comes first. The engine takes the income you entered, subtracts the standard deduction for your filing status ($16,100 single, $32,200 married filing jointly for 2026), and floors the result at zero. That taxable figure then passes through the 2026 federal brackets one band at a time: 10% on the portion in the first band, 12% on the portion in the second, and so on. The bracket table under the result shows only the bands your income actually reaches, with the dollars sitting in each.

The marginal rate reported is the rate of the highest band your taxable income lands in. The effective rate is total tax divided by the income you typed in, so both federal and state tax are in the numerator and the pre-deduction income is in the denominator.

State tax is worked out from the income you entered, not from the federal taxable figure. If the state publishes a standard deduction, the engine subtracts that state figure and applies the state flat rate to what is left. States with no individual income tax on wages return zero with a note saying so.

Why does the state figure sometimes say "not calculated"?

Because a top marginal rate is not a bracket table. For a graduated state the site publishes the top rate only, and applying that rate to every dollar of income would overstate the bill badly. Rather than publish a wrong number, the tool returns nothing and explains the gap in the caveat under the result.

The size of the error being avoided is large. California top rate is 13.3%. Multiplying $90,000 by 13.3% gives $11,970 of supposed state tax, which is not close to what a $90,000 California filer owes. New York top rate is 10.9% and the same trap applies.

Flat states and no-tax states can be computed exactly, so they get a number. That is the whole rule.

What does a full calculation look like?

A single filer with $90,000 of income living in Arizona. Every line below is what the tool produces.

The last two rows are the point of the exercise. The marginal rate is 22% and the effective rate is 14.46%, and the reason is visible in the middle of the table: only $23,500 of the $90,000 is taxed at 22%.

How much does the state change the answer?

A lot, and not always in the direction people expect. The federal figure is identical in every row below because the federal calculation does not care where you live. Only the state line moves.

Michigan sits above Colorado despite the lower rate, because Colorado publishes a $16,100 standard deduction and Michigan does not publish one, so the whole $90,000 is taxed. Rate alone does not rank states. The allowance underneath it does half the work, which is the same reason states with no income tax usually recoup the money through sales and property tax instead.

How do I read the result properly?

1. Type your income before the standard deduction into Annual income, before deductions.
2. Set Filing status. Only Single and Married filing jointly are offered; there is no head of household option.
3. Pick a State, or leave it unset to see the federal figure alone.
4. Read the headline. If it says "Federal and state income tax" the state figure is included. If it says "Federal income tax", the state was graduated and nothing was added.
5. Check the bracket table. The dollars in each band should add up to your taxable income, and the tax column should add up to the federal figure.
6. Compare the marginal rate against the effective rate before you make any decision about a raise or a deduction. A deduction saves you tax at the marginal rate, not the effective one.

Common mistakes

Entering income after the standard deduction. The field name says taxable income, the engine behaves as if you gave it income before the deduction. Entering $73,900 for a single filer produces a federal figure of $7,428 rather than $10,970. If you already subtracted the deduction, add it back before typing.

Reading the answer as your tax bill. This is tax on income, not a return. It contains no child tax credit, no education credit, no earned income credit, no capital gains treatment and no self-employment tax. A filer with two children can owe thousands less than this figure shows.

Assuming a raise is taxed at your top rate on all of it. Only the dollars above the bracket edge are taxed at the higher rate. The bracket table under the result shows exactly where the edges sit for your income.

Treating "not calculated" as "no state tax". It means the site does not hold enough data to answer, not that the state takes nothing. Only the states that return an explicit $0 levy no wage income tax.

Using the effective rate as a withholding target. The effective rate here covers income tax only. FICA is a further 7.65% on wages up to the Social Security base, which the paycheck calculator includes and this one does not.

Where this tool stops

It does not model itemized deductions, so anyone with large mortgage interest, state tax paid or charitable giving should enter income minus their itemized total and treat the result as approximate. It does not model the alternative minimum tax, capital gains rates, or the qualified business income deduction.

It uses one state standard deduction figure per state, applied whatever filing status you pick. Several states publish a higher allowance for joint filers, and this tool does not, so joint filers in flat states will see a slightly overstated state figure.

It is also not a filing tool. It produces an estimate you can sanity check a return against, not a number to put on a form. For that, work from the return itself or from tax software that asks about your credits.

Before you rely on the figure

• Confirm you entered income before the standard deduction, not after
• Check the filing status matches the one you will actually file under
• Add any credits you expect to claim, which reduce the tax dollar for dollar
• If you itemize, subtract your itemized total from income before entering it
• Note whether the state line was calculated or refused
• Add FICA separately if you are trying to reach a take-home figure
• Compare the federal line against last year Form 1040 line for total tax

Federal brackets and the standard deduction are inflation adjusted each year, so a figure from one tax year should never be reused in the next. State flat rates have been moving quickly: several states have scheduled step-downs in their rate over the next few years, and a rate that was right in January may not be right in December.